Halation-prevention filter, image analysis device equipped with said halation-prevention filter, and diffraction pattern intensity analysis method and diffraction pattern intensity correction program that use said halation-prevention filter

ABSTRACT

An image analysis device  1  is equipped with the photoreceptive means  11  that optically acquires diffraction pattern A that appears on the fluorescent screen  24  in order to obtain the diffraction pattern resulting from reflection high-energy electron diffraction, and the halation-prevention filter  12  provided so as to transmit the visible light emitted from the diffraction pattern A of the fluorescent screen  24,  along the light path connecting the photoreceptive means  11  and the fluorescent screen  24.  Also, the filter  12  is varied so that the transmittance of the visible light transmitted through the filter  12  is minimum at the filter center and increases with the distance from the center.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a device that analyzesdiffraction patterns resulting from reflection high-energy electrondiffraction and an intensity analysis method, and it particularlyrelates to a halation-prevention filter that prevents diffractionpattern halation, an image analysis device equipped with thehalation-prevention filter, and a diffraction pattern intensity analysismethod and a diffraction pattern intensity correction program that usethe halation-prevention filter.

[0003] 2. Description of Related Art

[0004] Reflection high-energy electron diffraction is an analyticaltechnique widely used in the molecular beam epitaxy field, as atechnique for monitoring in real time the growth state, when growingcrystals (e.g., metals, semiconductors) in vacuo.

[0005] In particular, ever since it was discovered that theatomic-layer-by-atomic-layer growth of crystals was observable bymeasuring the intensity of specular reflection point(s) in reflectionhigh-energy electron diffraction, reflection high-energy electrondiffraction has been recognized as a useful method for controllingcrystal growth at the atomic layer level, so it has been applied tovarious industries (e.g., semiconductor device fabrication).

[0006] However, in image analysis devices that use the diffractionpatterns resulting from conventional reflection high-energy electrondiffraction, when a diffraction pattern is photographed, the intensitiesof the specular reflection point(s) are much greater than theintensities of the surrounding diffraction points and Kikuchi pattern,so the vicinity of the specular reflection point(s) produces halation.This becomes particularly significant when the entire diffractionpattern is photographed, and if the light exposure is decreased duringphotography in order to avoid halation, the following drawback results:the surrounding diffraction points and the Kikuchi pattern becomeunobservable because of the insufficient intensity (light intensity).

[0007] This problem frequently restricts, to the region between thespecular reflection point(s) and the zero-order Laue zone, theconventional CCD camera-based observation of the diffraction patternresulting from reflection high-energy electron diffraction, as the onlyway to avoid halation without decreasing the light exposure. However,when such an observation technique is used, the diffraction patterninformation from outside the zero-order Laue zone is undetected, so aproblem different from the aforementioned drawback is confronted: it isimpossible to accurately analyze the sample state.

[0008] In a technique sometimes adopted in order to prevent the halationthat occurs in a diffraction pattern when using a camera to photographthe diffraction pattern resulting from reflection high-energy electrondiffraction, masking is performed when printing the photographicprinting paper instead of in the photography state, thereby yielding adiffraction pattern with good contrast. This technique has a problem,however, in that linear intensity analysis is impossible because anirreversible correction is applied to the light intensity, which isessential for intensity analysis.

[0009] As another device configuration measure that prevents halation,there is a technique that uses sectors with a masking part and atransmissive part, between the fluorescent screen and the measurementsample in the vacuum chamber. To be more specific, in a sector, themasking part is configured by using a blade or vane with a geometricallycomputed shape. Furthermore, by making the electron beam, which isdiffracted in the vicinity of the surface of the measurement sample,pass through the sector in which this blade rotates, the sectorfunctions to inhibit halation near the center by physically decreasingthe amount of electron beam passing through.

[0010] Actually, however, the mere adherence of minute dust particles onthe blade markedly attenuates the intensity in the rotating partcorresponding to this dust's position. An a result, this intensityattenuation affects the electron beam that forms the diffractionpattern, so the diffraction pattern does not accurately reflect thestructure of the material. Consequently, not only must the blade bemanufactured precisely, but it must be clean. Actually, however, theincreased complexity of the adopted rotary mechanism also adds to thedifficulty of completely eliminating dust, etc. From the standpoint ofmeasurement precision, therefore, diffraction intensity analysis bymeans of such sectors set in vacuo is undesirable.

[0011] Furthermore, although Japanese Unexamined Patent Publication No.7-6967 discloses an observation device that uses reflection high-energyelectron diffraction, it merely suggests a configuration that uses afilter that selectively transmits only light of a specific wavelength.That is, it is based on the idea of handling as a bundle the lightincident on the filter, but there is no suggestion of the idea ofincrementally varying the light transmittance.

SUMMARY OF THE INVENTION

[0012] The present invention relates to a device that analyzesdiffraction patterns resulting from reflection high-energy electrondiffraction and an intensity analysis method, and it particularlyrelates to a halation-prevention filter that prevents diffractionpattern halation, an image analysis device equipped with thehalation-prevention filter, and a diffraction pattern intensity analysismethod and a diffraction pattern intensity correction program that usethe halation-prevention filter. The halation-prevention filter isconfigured such that a transmittance of the visible light transmittedthrough the filter is lowest at a center of said filter and increaseswith a distance from said center. The present invention implements imageanalysis that enables the acquisition of diffraction patterns withouthalation and with good contrast. It also aims at implementing imageanalysis that enables the analysis of the intensity at all points in anobtained diffraction pattern.

BRIEF DESCRIPTION OF THE DRAWING

[0013]FIG. 1 shows an overall schematic diagram showing one example ofthe image analysis device of the first embodiment of the presentinvention.

[0014]FIG. 2 shows a photograph showing one example of thehalation-prevention filter shown in FIG. 1.

[0015]FIG. 3 shows an overall schematic diagram showing one example ofthe image analysis device of the second embodiment of the presentinvention.

[0016]FIG. 4 shows a schematic diagram showing one example of the imageanalysis device of the third embodiment of the present invention.

[0017]FIG. 5 shows a functional block diagram of the diffraction patternintensity correction means equipped with the image analysis device shownin FIG. 4.

[0018]FIG. 6 shows a data structure diagram for the measurementintensity storage means equipped with the diffraction pattern intensitycorrection means shown in FIG. 5.

[0019]FIG. 7 shows a functional block diagram showing an example of thedeformation of the diffraction pattern intensity correction means shownin FIG. 5.

[0020] FIGS. 8(a) through 8(c) show photographs showing an example ofthe diffraction pattern, which were photographed without using thehalation-prevention filter of the present invention.

[0021]FIG. 9 shows a photograph showing an example of the diffractionpattern photographed by using the halation-prevention filter of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] To achieve the purposes, the present invention adopts ahalation-prevention filter that is provided so as to transmit thevisible light emitted from the diffraction pattern of the fluorescentscreen, along the light path that connects the fluorescent screen onwhich the diffraction pattern appears as the result of reflectionhigh-energy electron diffraction and the photoreceptive means thatoptically acquires the diffraction pattern. Also, the transmittance ofthe visible light transmitted through the filter is varied so as to belowest at the center of the filter and to increase with the distancefrom the center.

[0023] According to the present invention, by varying the filtertransmittance so that it is lowest at the filter center and increaseswith the distance from the center, it is possible to decrease thecentral intensity, thereby minimizing the difference in intensitybetween the center and the peripheral areas, even for diffractionpatterns with a high central intensity.

[0024] Also, in the present invention, the configuration is such thatthe transmittance increases in proportion to r^(n), where r is thedistance from the filter center.

[0025] According to the present invention, the transmittance increasesin proportion to the n^(th) power of r, the distance from the filtercenter, so the present invention can eliminate the smoothing orflattening of transmittance near the center, in intermediate regions,and elsewhere.

[0026] The present invention also adopts an image analysis deviceequipped with a photoreceptive means that optically acquires thediffraction pattern appearing on the fluorescent screen used to obtainthe diffraction pattern resulting from reflection high-energy electrondiffraction, and it adopts a halation-prevention filter that is providedso as to transmit the visible light emitted from the diffraction patternof the fluorescent screen, along the light path connecting thephotoreceptive means and the fluorescent screen.

[0027] The filter varies the transmittance of the visible lighttransmitted through the filter, so that it is lowest at the center ofthe filter and increases with the distance from the center.

[0028] According to the present invention, by varying the filtertransmittance so that it is lowest at the filter center and increaseswith the distance from the center, it is possible to decrease thecentral intensity, thereby minimizing the difference in intensitybetween the center and the peripheral areas, even for diffractionpatterns with high central intensity.

[0029] The invention is configured so that the transmittance increasesin proportion to r^(n), where r is the distance from the filter center.

[0030] According to the present invention, the transmittance increasesin proportion to the n^(th) power of r, the distance from the filtercenter, so the present invention can eliminate the smoothing oftransmittance near the center, in intermediate regions, and elsewhere.

[0031] The invention is also configured so that it has an in-plane orin-planar movement means that moves the halation-prevention filter inthe plane orthogonal to the light path.

[0032] The present invention has an in-plane or in-planar or in-planarmovement means, so it is possible to move the center of thehalation-prevention filter.

[0033] The invention is also configured so that, in the image analysisdevice described, it is equipped with a photoemissive means thatgenerates a point light source; an emission control means that controlsthe generation of the point light source of the photoemissive means; anintensity measurement means that measures, via the photoreceptive means,the intensity of the visible light emitted from the diffraction patternof the fluorescent screen as well as the intensity of the visible lightemitted from the point light source, that passes through the filter; anintensity decrease rate computation means that computes the rate ofdecrease in the intensity of the visible light transmitted through thefilter, based on the intensity of the visible light emitted by the pointlight source, that was measured by the intensity measurement means; anda corrected-intensity computation means that computes the correctedintensity used to correct the intensity of the visible light emittedfrom the diffraction pattern of the fluorescent screen, that wasmeasured by the photoreceptive means.

[0034] According to the present invention, the rate of decrease in theintensity of the visible light transmitted through the filter iscomputed, and, based on the rate of decrease, the corrected intensityresulting from the correction of the intensity of the visible lightemitted from the diffraction pattern of the fluorescent screen iscomputed, so it is possible to obtain the intensity of the visible lightactually emitted from the diffraction pattern of the fluorescent screen.

[0035] The invention also adopts the diffraction pattern intensityanalysis method used to analyze the intensity of the visible lightemitted from the diffraction pattern of the fluorescent screen as aresult of reflection high-energy electron diffraction; and the methodhas a process that utilizes the photoreceptive means to measure theintensity of the diffraction pattern that appears on the fluorescentscreen, via a halation-prevention filter such that the transmittance isminimum at the filter center and the transmittance increases with thedistance from the center; a process that utilizes the photoreceptivemeans to measure the intensity of the point light source, via thefilter, and obtains the rate of decrease in the intensity of the visiblelight transmitted through the filter, based on the measured results; anda process that, based on the rate of decrease, corrects the diffractionpattern intensity that was measured by the photoreceptive means.

[0036] According to the present invention, it is equipped with a processthat measures the intensity of the diffraction pattern, via ahalation-prevention filter that is varied so that the transmittanceincreases with the distance from the center, a process that obtains therate of decrease in the intensity attributable to the filter, and aprocess that corrects the intensity of the diffraction pattern based onthe decrease rate, so it is possible to obtain the intensity of thevisible light actually emitted from the diffraction pattern.

[0037] The invention is configured so that the transmittance of thevisible light transmitted through the filter increases in proportion tothe n^(th) power of r, where r is the distance from the filter center.

[0038] According to the present invention, the transmittance increasesin proportion to the n^(th) power of r, the distance from the filtercenter, so it is possible to optimally control the contrast over theentire diffraction pattern.

[0039] The invention implements a measured intensity storage means thatstores the intensity of the visible light emitted from the diffractionpattern of a fluorescent screen, that was measured by the photoreceptivemeans after the light passed through a halation-prevention filter thatis varied so that the transmittance when transmitting the visible lightemitted from the diffraction pattern of a fluorescent screen as theresult of the transmittance of the reflection high-energy electrondiffraction is minimum at the filter center and increases with thedistance from the center; an intensity decrease rate storage means thatstores the rate of decrease in the intensity of the visible light thatpasses through the halation-prevention filter; and a corrected-intensitycomputation means that computes the corrected intensity of thediffraction pattern by correcting the intensity stored by the measuredintensity storage means, based on the decrease rate stored by theintensity decrease rate storage means.

[0040] The present invention implements a measured intensity storagemeans that stores the diffraction pattern intensity measured by thephotoreceptive means after the light passes through thehalation-prevention filter that is varied so that the transmittanceincreases with the distance from the center; an intensity decrease ratestorage means that stores the rate of decrease in the intensity of thevisible light that passes through the halation-prevention filter; and acorrected-intensity computation means that computes the correctedintensity of the diffraction pattern by correcting the intensity storedby the measured intensity storage means, based on the decrease ratestored by the intensity decrease rate storage means. So, it is possibleto correct the intensity of the diffraction pattern obtained via thehalation-prevention filter.

[0041] The invention implements an intensity measurement means thatmeasures the intensity of the visible light emitted by the point lightsource, that is measured by the photoreceptive means, via thehalation-prevention filter that is changed so that the transmittancewhen transmitting the visible light emitted from the diffraction patternof the fluorescent screen as the result of the transmittance of thereflection high-energy electron diffraction is minimum at the filtercenter and increases with the distance from the center; an intensitydecrease rate computation means that computes the decrease rate, basedon the intensity measured by the intensity measurement means and thereference intensity of the visible light that is emitted from the pointlight source but does not pass through the halation-prevention filter;an intensity decrease rate storage means that stores the decrease ratecomputed by the intensity decrease rate computation means; a measuredintensity storage means that stores the intensity of the visible lightemitted from the diffraction pattern of the fluorescent screen, that ismeasured by the photoreceptive means, via the halation-preventionfilter; and a corrected-intensity computation means that computes thecorrected intensity of the diffraction pattern by correcting theintensity stored by the measured intensity storage means, based on thedecrease rate stored by the intensity decrease rate storage means.

[0042] The present invention implements an intensity measurement meansthat measures the intensity of the point light source, that is measuredby the photoreceptive means, via the halation-prevention filter that ischanged so that the transmittance increases with the distance from thecenter; an intensity decrease rate computation means that computes thedecrease rate, based on the measured intensity and the referenceintensity of the point light source that does not pass through thehalation-prevention filter; an intensity decrease rate storage meansthat stores this decrease rate; a measured intensity storage means thatstores the diffraction pattern intensity measured by the photoreceptivemeans, via the halation-prevention filter; and a corrected-intensitycomputation means that computes the corrected intensity of thediffraction pattern, based on the decrease rate stored by the intensitydecrease rate storage means. So, it is possible to correct the intensityof the diffraction pattern obtained via the halation-prevention filter,according to the environment in which the halation-prevention filter isused. In this manner, the present invention attempts to achieve theaforementioned purposes.

[0043] Next, one embodiment of the present invention will be explained,with reference to FIGS. 1 and 2. Here, FIG. 1 is an overall schematicdiagram of one example of the image analysis device 1 of the presentembodiment. FIG. 2 is a photograph showing one example ofhalation-prevention filter 12 used in image analysis device 1.

[0044] As shown in FIG. 1, the image analysis device 1 of the presentembodiment is equipped with photoreceptive means 11 that opticallyacquires the diffraction pattern that appears on the fluorescent screen24 for obtaining the diffraction pattern that results from reflectionhigh-energy electron diffraction as well as with halation-preventionfilter 12 that is provided, so as to transmit the visible light emittedfrom the diffraction pattern of the fluorescent screen, along the lightpath connecting the photoreceptive means 11 and the fluorescent screen24. Furthermore, in FIG. 1, A represents the diffraction pattern.

[0045] To explain this in detail, in FIG. 1, the reflection high-energyelectron diffraction device 2 is equipped with the vacuum chamber 22 inwhich is mounted the sample holder 21 that holds the measurement sample3, the electron gun 23 that exposes the measurement sample 3 to anelectron beam, and a fluorescent screen 24 on which appears thediffraction pattern resulting from the diffraction on the surface of themeasurement sample 3.

[0046] As aforementioned, the image analysis device 1 is equipped withthe photoreceptive means 11 that optically acquires the diffractionpattern appearing on the fluorescent screen 24 and thehalation-prevention filter 12.

[0047] Here, the photoreceptive means 11 is the means of photographing,as moving images or still pictures, the diffraction pattern appearing onthe fluorescent screen 24. Examples include a CCD camera, video camera,optical camera, etc. In photography by means of photoreceptive means 11,when conducting so-called in situ observation, which is used to observechanges in the crystal structures on the surface of the measurementsample 3 in the vacuum chamber, moving-picture photography is selected;when performing diffraction intensity analysis of the intensity of anobtained diffraction pattern, still-picture or moving-picturephotography is selected.

[0048] As aforementioned, the halation-prevention filter 12 is providedin order to transmit the visible light emitted from the diffractionpattern on the fluorescent screen, along the light path connecting thefluorescent screen 24 on which the diffraction pattern appears as theresult of reflection high-energy electron diffraction and thephotoreceptive means 11 that optically acquires the diffraction pattern.It is varied so that the transmittance of the visible light transmittedthrough the filter 12 is minimum at the filter center and increases withthe distance from the center. Furthermore, the transmittance indicateshow much incident light is transmitted. 100% transmittance meanstransmission without modification and without light intensity reduction.

[0049] To be specific, the transmittance of the filter 12 is set so asto increase in proportion the r^(n), where r is the distance from thecenter of the filter 12. That is, when light of location-independent,uniform intensity is transmitted to the filter, in the observed plane,the transmittance of the light density at in-plane or in-planar distancer from the center correlates proportionally to r^(n).

[0050] The filter 12 is obtained by printing a gradient pattern on anoptically transparent sheet or plate. Such a gradient pattern is readilyobtainable by means of fine computer graphics. For example, the filter12 can be fabricated by means of a technique that prints a gradientpattern on a transparent sheet.

[0051] One example of a concrete embodiment of this halation-preventionfilter 12 is shown in FIG. 2. As shown in FIG. 2, the filter 12 has agradient pattern that varies from the center to the periphery. Here, thefilter 12 shown in FIG. 2 has the pattern that assumes that n=0.5, asthe correlation with the aforementioned distance, and the transmittancegradient is such that the transmittance is lowest at the filter centerand the transmittance at distance r from the center is r^(0.5).

[0052] n=0.5 was derived as the result of tests conducted by theinventor of the present application, based on the fact that a CCD camerahas a wider intensity dynamic range than does an optical camera. On theother hand, in the case of an optical camera, it is preferable to setn=3, as the attribute that maximizes the effectiveness of the filter 12.

[0053] Furthermore, as shown in FIG. 1, the filter 12 is positionedbetween the fluorescent screen 24 and a CCD camera, the photoreceptivemeans 11. In the present embodiment, if the fluorescent screen 24 has adiameter within the range from 100 mm to 200 mm, the distance from thefluorescent screen 24 to the CCD camera 11 is set within the range from200 mm to 500 mm.

[0054] Next, the process used to obtain the diffraction pattern in thepresent embodiment will be explained. First, the measurement sample 3 tobe measured is mounted in the sample holder 21. After the measurementsample 3 is placed in the sample holder 21, the interior of the vacuumchamber 22 is evacuated to the predetermined degree of vacuum. Then, themeasurement sample 3 is exposed to the incident electron beam from theelectron gun 23.

[0055] This incident electron beam is incident at a very small anglerelative to the measured surface of measurement sample 3. Then theincident electron beam is reflected and diffracted by the atoms near thesurface of the measurement sample 3. The incident electron beam isincident at a very small angle, so the measurement is surface sensitive.The reflected and diffracted electron beam produces an emissionphenomenon in the fluorescent screen 24, so a spotted diffractionpattern corresponding to the atomic structure in the vicinity of thesurface appears on the fluorescent screen 24.

[0056] The diffraction pattern that appears on this fluorescent screen24 is obtained optically, via the filter 12, by means of thephotoreceptive means 11. When the diffraction pattern is obtained, it isalso possible to obtain in real time a sensitive diffraction pattern inthe surface atomic structure of the measurement sample.

[0057] Here, when a photoreceptive means 11 (e.g., a CCD camera) thatrequires focusing is used, photographs are taken with the focus of theCCD camera 11 set for the fluorescent screen 24, so the pattern of thefilter 12 does not appear directly on the photographed image. Thedecrease in the amount (i.e., intensity) of the visible light capturedby the CCD camera 11 is reflected in the image, in the shapecorresponding to the transmittance of the filter 12.

[0058] As a result, the CCD camera 11 is not focused on the filter 12,so even if the gradient pattern's resolution is somewhat low, the lowresolution has minimal effect on the image photographed through thefilter 12. So, during the manufacture of the filter 12 of the presentembodiment, high pattern precision is not required, so it can bemanufactured easily and inexpensively, which can be considered anadvantage.

[0059] As explained previously, in the present embodiment, by varyingthe filter transmittance so that it is lowest at the filter center andincreases with the distance from the center, it is possible to minimizethe difference in intensity between the center and the peripheral areaby decreasing the intensity of the central area, even in diffractionpatterns with a high central intensity. Furthermore, even if the entirediffraction pattern is optically acquired, it is possible to provide anenvironment in which the entire, halation-free diffraction pattern canbe obtained.

[0060] Also, in the photoreceptive means, it is possible to control theintensity of the visible light emitted from the diffraction pattern ofthe fluorescent screen, within the allowable, halation-freephotoreceptive range.

[0061] Furthermore, because the transmittance increases in proportion tothe n^(th) power of r, the distance from the filter center, it ispossible to eliminate the smoothing of transmittance near the center, inintermediate regions, and elsewhere. Furthermore, it is possible to makethe transmittance highly distance dependent, so it is possible toeffectively and sufficiently reduce light intensity in the vicinity ofthe center, compared with that in the periphery.

[0062] Next, the second embodiment of the present invention will beexplained with reference to FIG. 3. Here, components with the samestructure as in the aforementioned first embodiment are keyed with thesame symbols, so redundant descriptions are omitted. FIG. 3 is theoverall schematic diagram showing the image analysis device 4 of thepresent embodiment.

[0063] In the present embodiment, the image analysis device 4 has, inaddition to the configuration of the aforementioned first embodiment,the in-plane or in-planar movement means 13 and the in-plane orin-planar movement means 14 that move the halation-prevention filter 12in the plane orthogonal to the light path connecting the photoreceptivemeans 11 and the fluorescent screen 24. However, in order to enablemovement of the filter 12 to any in-plane or in-planar position, thein-plane or in-planar movement means 13 and the in-plane or in-planarmovement means 14 move the filter 12 in different directions.

[0064] Such an in-plane or in-planar movement means is provided because,in the normal photography of reflection high-energy electron diffractionpatterns, the specular reflection point(s) are positioned about halfwayfrom the image center, so the position varies depending on thephotography conditions.

[0065] Next, the present embodiment will be explained in detail. Asshown in FIG. 3, the image analysis device 4 of the present embodimentis equipped with the x-direction in-plane or in-planar movement means 13that moves the filter 12 in the x-direction in the figure and they-direction in-plane or in-planar movement means 14 that moves thefilter 12 in the y-direction in the figure, in the plane orthogonal tothe light path connecting the photoreceptive means 11 and thefluorescent screen 24.

[0066] The x-direction in-plane or in-planar movement means 13 iscomposed of the x-direction movement element 13 a that supports thefilter 12, the x-direction lead screw shaft member 13 b, the x-directiondrive motor 13 c, and the x-direction lead screw shaft bearing 13 d.

[0067] Here, a through-hole is provided within the x-direction movementelement 13 a, and a female screw corresponding to the male screw partformed in the surface of the x-direction lead screw shaft member 13 b isprovided on the surface within this through-hole. Furthermore, one endof the x-direction lead screw shaft member 13 b is supported by thebearing 13 d, and the other end is connected to the x-direction drivemotor 13 c. This rotates forward and backward the x-direction drivemotor 13 c, thereby controlling the movement of filter 12 in thex-direction.

[0068] Similarly, the y-direction in-plane or in-planar movement means14 is composed of the y-direction movement element 14 a that supportsthe filter 12, the y-direction lead screw shaft member 14 b, they-direction drive motor 14 c, and the y-direction lead screw shaftbearing 14 d.

[0069] A through-hole is provided within the y-direction movementelement 14 a, and a female screw corresponding to the male screw partformed in the surface of y-direction lead screw shaft member 14 b isprovided on the surface within this through-hole. Furthermore, one endof the y-direction lead screw shaft member 14 b is supported by thebearing 14 d, and the other end is connected to the y-direction drivemotor 14 c. This rotates forward and backward the y-direction drivemotor 14 c, thereby controlling the movement of filter 12 in they-direction.

[0070] During the use of the image analysis device 4 of the presentembodiment, the photoreceptive means 11 obtains the diffraction patternby controlling the aforementioned x-direction in-plane or in-planarmovement means 13 and the y-direction in-plane or in-planar movementmeans 14, in order to align the center of the filter 12, wheretransmittance is lowest, with the position(s) of the specular reflectionpoint(s) of the diffraction pattern.

[0071] To be specific, while a fixed distance is maintained between thefluorescent screen 24 and the filter 12 and between the filter 12 andthe photoreceptive means 11, the x-direction drive motor 13 c and they-direction drive motor 14 c are rotated in order to move thex-direction movement element 13 a and the y-direction movement element14 a. For example, the filter position is set so that the filter centeris aligned with the specular reflection point(s) of the fluorescentscreen 24, when the diffraction pattern is viewed from thephotoreceptive means 11, while displaying the image photographed by thephotoreceptive means 11 on a monitor, etc. Then, the photoreceptivemeans 11 is used to photograph the diffraction pattern that appears onthe fluorescent screen 24, via the center-aligned filter 12.

[0072] As explained previously, in the present embodiment has in-planeor in-planar movement means 13 and 14, so it is possible to move thecenter of the halation-prevention filter 12, thereby enabling theacquisition of the diffraction pattern appropriate to the displacementof the specular reflection point(s), which depends on the incidentdirection of the electron beam causing reflection high-energy electrondiffraction. Furthermore, it is possible to provide an image analysisdevice 4 equipped with a highly flexible halation-prevention mechanism.

[0073] Next, the third embodiment of the present invention will beexplained with reference to FIG. 1 and FIGS. 4-6. Here, components withthe same structure as in the aforementioned embodiment are keyed withthe same symbols, so redundant descriptions are omitted. Also, FIG. 4 isa schematic diagram showing the image analysis device 5 of the presentembodiment. FIG. 5 is a functional block diagram of the diffractionpattern intensity correction means 16 equipped with the image analysisdevice 5. FIG. 6 is a data structure diagram of the measured intensitystorage means 35 equipped with the diffraction pattern intensitycorrection means 16. Furthermore, in FIG. 4, represents the point lightsource.

[0074] The present embodiment was invented based on the realization ofthe fact that it is effective to take into consideration the effect ofthe filter 12 on the intensity of the visible light that is passedthrough the filter 12, in order to increase the accuracy of theintensity analysis that uses the image analysis device, when aconfiguration that prevents halation by obtaining a diffraction patternthrough the filter 12 is adopted, as in the aforementioned first andsecond embodiments.

[0075] As shown in FIGS. 4 and 5, in addition to the basic structure(see FIG. 1) of the reflection high-energy electron diffraction device 2with fluorescent screen 24 that was explained in the aforementionedfirst embodiment, the image analysis device 5 of the present embodimentis equipped with the photoemissive means 15 that generates the pointlight source, the emission control means 31 that controls the generationof the point light source of the photoemissive means 15, the intensitymeasurement means 32 that measures, via the photoreceptive means 11, theintensity through the filter 12 of the visible light emitted from thediffraction pattern of the fluorescent screen and the intensity throughthe filter 12 of the visible light emitted by the point light source,the intensity decrease rate computation means 33 that computes the rateof decrease in the intensity of the visible light transmitted throughthe filter 12, based on the intensity of the visible light emitted bythe point light source, that was measured by the intensity measurementmeans 32, and the corrected-intensity computation means 36 that computesthe corrected intensity obtained by correcting the intensity, asmeasured by the photoreceptive means 11, of the visible light emittedfrom the diffraction pattern of the fluorescent screen, based on thedecrease rate computed by the intensity decrease rate computation means33.

[0076] To be more specific, the photoemissive means 15 is the means(e.g., a liquid-crystal panel) of generating a point light source at anyposition, under the control of the emission control means 31 describedlater. As shown in FIG. 4, it is desirable to provide a detachablephotoemissive means 15 where the fluorescent screen 24 is configured inthe first embodiment. This is done in order to obtain the correctionparameters in the environment in which the diffraction pattern isactually obtained, thereby enabling the most accurate correction.

[0077] Here, when adopting a method of mounting the photoemissive means15 at the location where the fluorescent screen 24 is placed (e.g., byoverlapping the fluorescent screen 24 with the photoemissive means 15),it is necessary to minimize the measurement condition error caused by animperfect alignment with the placement position of the fluorescentscreen 24. Concretely, the condition should be that [the error] iswithin the error range that is allowable in the later-mentionedcorrection, which takes into consideration the intensity decrease.

[0078] That is, as shown in FIG. 4, the distance between thephotoemissive means 15 and the photoreceptive means 11 is adjusted sothat it equals the distance (see FIG. 1) between the photoreceptivemeans 11 and the fluorescent screen 24 when obtaining the diffractionpattern, and the spacing between the photoreceptive means 11 and filter12 when photographing the point light source is adjusted so that itequals the distance between the photoreceptive means 11 and the filter12 when obtaining the diffraction pattern. However, it also is possibleto adopt a method that approximates the corrected intensity, by adoptinga configuration that yields an interrelationship similar to thepositional relationship among the fluorescent screen 24, the filter 12,and the photoreceptive means 11.

[0079] Also, the emission control means 31, the intensity measurementmeans 32, the intensity decrease rate computation means 33, theintensity decrease rate storage means 34, the measured intensity storagemeans 35, and the corrected-intensity computation means 36 shown in FIG.5 are implemented by the processing means and the storage means (notshown) that are provided in the diffraction pattern intensity correctionmeans 16, which is equipped with the image analysis device 5.Furthermore, as the diffraction pattern intensity correction means 16equipped with these means, an information processing device (e.g., apersonal computer) that also analyzes the image information obtained bythe photoreceptive means 11 is assumed.

[0080] The storage means is the means of storing information in a givenregion. Examples include so-called memory (e.g., RAM), storage media(e.g., HDD, CD-R), etc. However, it is not limited to a specific medium,and a configuration that combines multiple storage media may also beused.

[0081] Also, the processing means is a means of processing informationthat includes a computation means (e.g., a CPU), and it controlsoperations such as the input/output interface (not shown) that receivesimage information from the photoreceptive means and the aforementionedstorage means, etc. However, it is not limited to a configuration thatconsists solely of one specific computation means, but it also may beconfigured with multiple computation means that enable the parallelprocessing of information.

[0082] The processing means implements the aforementioned emissioncontrol means 31, the intensity measurement means 32, the intensitydecrease rate computation means 33, and the corrected-intensitycomputation means 36, when processing is initiated by external commands,etc., according to the diffraction pattern intensity correction programstored in a specific region of the storage means.

[0083] Here, the emission control means 31 is the means of controllingthe generation of the point light source in the photoemissive means 15.By controlling so that the emission control means 31 emits light of aspecific intensity at any point of the photoemissive means 15, it ispossible to set at any position the point light source that emits thereference intensity, which is the reference for computing the intensitydecrease rate mentioned later.

[0084] The intensity measurement means 32 is the means of obtaining theintensity (i.e., amount) of visible light at a specific point in theimage information, based on the image information obtained by thephotoreceptive means 11. The intensity measurement means 32 is used tomeasure not only the intensity of the light emitted by the point lightsource, but also to measure the intensity of the light emitted from thediffraction pattern of the aforementioned fluorescent screen.

[0085] The intensity decrease rate computation means 33 is the means ofcomputing the rate of decrease in the point light source intensity,which is reduced by passing through the filter. Here, the intensitydecrease rate is the parameter that represents how much the lightemitted at any position is decreased by passing through the filter 12with a varied transmittance, and it means that, when the intensitydecrease rate is 0%, the intensity is not reduced by the filter 12, sothe light intensity is not attenuated.

[0086] To be more specific, based on the point light source intensitymeasured by the intensity measurement means 32 and the theoretical ormeasured reference intensity of the visible light emitted by the pointlight source when it did not pass through the halation-prevention filter12, the means computes how much the intensity of the visible light dropsafter passing through the filter 12, compared with the case where thefilter 12 is not provided.

[0087] The intensity decrease rate storage means 34 is the means ofstoring the intensity decrease rate computed by the intensity decreaserate computation means 33, in predetermined areas in the aforementionedstorage means (not shown), and it stores the intensity decrease rate byassociating it with the point light source position (i.e., the specificpositional coordinates on the fluorescent screen 24).

[0088] The measured intensity storage means 35 is the means of storingthe intensity of the visible light emitted from the target, that ismeasured by the photoreceptive means 11, in a specific area in theaforementioned storage means (not shown). In the present embodiment, theintensity measurement means 32 stores the intensity of the diffractionpattern in cases where the diffraction pattern is measured after thelight passes through the filter 12.

[0089] The corrected-intensity computation means 36 is the means ofcomputing corrected intensities, for the intensities of the diffractionpatterns stored by the measured intensity storage means 35, based on theintensity decrease rates stored by the intensity decrease rate storagemeans 34.

[0090] Furthermore, the external device 17 shown in FIG. 5 is a devicethat is connected to the diffraction pattern intensity correction means16 and that receives the intensities of diffraction patterns aftercorrections obtained by means of the diffraction pattern intensitycorrection means 16. Examples include display monitors, other measuringinstruments, etc.

[0091] By adopting the configuration of the present embodiment, it ispossible to provide an environment that enables the acquisition of theintensity of the visible light actually emitted from the diffractionpattern of the fluorescent screen and enables the accurate analysis ofthe intensity, because the rate of decrease in the intensity of thevisible light that passed through the filter is computed and, basedthereupon, the corrected intensity, which is determined by correctingthe intensity of the visible light emitted from the diffraction patternof the fluorescent screen, is computed.

[0092] Also, the diffraction pattern intensity analysis of the presentembodiment analyzes the intensity of the visible light emitted from thediffraction pattern of the fluorescent screen as the result ofreflection high-energy electron diffraction. Also, as the diffractionpattern intensity analysis method, a method with the following processeswas adopted: a process that utilizes the photoreceptive means 11 tomeasure the intensity of the diffraction pattern that appears on thefluorescent screen 24, via the halation-prevention filter 12 that isvaried so that the transmittance is lowest at the center of the filter12 and increases with the distance from the center; a process thatutilizes the photoreceptive means to measure the intensity of the pointlight source via the filter, and then obtains the rate of decrease inthe intensity of the visible light transmitted through the filter, basedon the measurement results; and a process that corrects the diffractionpattern intensity measured by the photoreceptive means, based on thedecrease rate.

[0093] When such a diffraction pattern intensity analysis method isadopted, it is possible to obtain the intensity of the visible lightactually emitted from the diffraction pattern of the fluorescent screen,because it has a process that measures the intensity of the diffractionpattern, through the halation-prevention filter that is varied so thatthe transmittance increases with the distance from the center, a processthat obtains the rate of intensity decrease caused by the filter, and aprocess that corrects the intensity of the diffraction pattern based onthe decrease rate. Furthermore, accurate intensity analysis is possible.

[0094] Next, the diffraction pattern intensity correction program thatimplements the aforementioned emission control means 31, the intensitymeasurement means 32, the intensity decrease rate computation means 33,the corrected-intensity computation means 36, etc., will be explained indetail.

[0095] The diffraction pattern intensity correction program of thepresent embodiment implements the intensity measurement means 32 thatmeasures the intensity of the visible light that is emitted by the pointlight source and is measured by the photoreceptive means 11, via thehalation-prevention filter 12 that is varied so that the transmittancewhen transmitting the visible light emitted from the diffraction patternof the fluorescent screen as the result of the transmittance of thereflection high-energy electron diffraction is minimum at the filtercenter and increases with the distance from the center; the intensitydecrease rate computation means 33 that computes the decrease rate,based on the intensity measured by the intensity measurement means 32and the reference intensity of the visible light that is emitted by thepoint light source but does not pass through the halation-preventionfilter 12; the intensity decrease rate storage means 34 that stores thedecrease rate computed by the intensity decrease rate computation means33; the measured intensity storage means 35 that stores the intensity ofthe visible light emitted from the diffraction pattern of thefluorescent screen, that passes through the halation-prevention filter12 and is measured by the photoreceptive means 11; and thecorrected-intensity computation means 36 that computes the correctedintensity of the diffraction pattern, by correcting the intensity storedby the intensity storage means 35, based on the decrease rate stored bythe intensity decrease rate storage means 34.

[0096] To be specific, the processing based on the aforementioneddiffraction pattern intensity correction program is as follows: Forlight emitted from any point (x, y) on the fluorescent screen 24, theintensity decrease rate T(x, y) of the filter following measurement byusing the photoreceptive means 11 is determined. Then thetransmission-corrected intensity I(x, y) is determined based on thediffraction pattern's intensity I_(C)(x,y), which was measured by usingthe photoreceptive means 11.

[0097] Hereinafter, processing based on the diffraction patternintensity correction program is divided broadly into processing thatcomputes the intensity decrease rate and processing the corrects thediffraction pattern intensity.

[0098] First, the sequence of processes used to compute the intensitydecrease rate will be explained. The intensity decrease rate computationmeans 33 initially determines the intensity I_(O) of the point lightsource used as the reference, after which it transfers the instructioninformation to the emission control means 31, in order to generate apoint light source of that intensity. Based on the transferredinstruction information, the emission control means 31 sends controlinformation to the photoemissive means 15, in order to generate thepoint light source emitted at given intensity I_(O) at given position(x1, y1). Based on the sent control information, the photoemissive means15 generates the reference point light source at the given position (x1,y1).

[0099] Then, the intensity measurement means 32 measures the intensityI_(oc)(x1, y1) of the point light source generated by the photoemissivemeans 15, via the photoreceptive means 11, with the transmittance-variedfilter installed. Subsequently, the intensity measurement means 32stores the measured intensity I_(OC)(x1, y1) of the point light sourcein a given region of the storage means, after which it transfers thestored intensity I_(OC)(x1,y1) to the intensity decrease ratecomputation means 33.

[0100] The intensity decrease rate computation means 33 that receivedthe intensity I_(OC)(x1, y1) (i.e., the measurement result) computes theintensity decrease rate T(x1, y1), based on the intensity I_(O)transferred to the emission control means 31 and the received intensityI_(OC)(x1, y1). The intensity decrease rate computation means 33transfers the computed intensity decrease rate T(x1, y1) to theintensity decrease rate storage means 34.

[0101] Subsequently, the intensity decrease rate storage means 34 storesby associating the intensity decrease rate T(x1, y1) computed by theintensity decrease rate computation means 33 and the positioncoordinates (x1, y1). Finally, intensity decrease rate storage means 34stores the intensity decrease rate T(x_(i), y_(i)) for each differentposition coordinates (x_(i), y_(i)) and functions as the database ofintensity decrease rates when the filter 12 is used.

[0102] Next, the relationship among the point light source's measuredintensity I_(OC)(x_(i), y_(i)), the reference intensity I_(O), and theintensity decrease rate T(x_(i), y_(i)) is as shown in the followingEquation 1.

T(x _(i) , y _(i))=I _(OC)(x _(i) , y _(i))/I _(O)  (1)

[0103] Furthermore, for the position coordinates (x_(i), y_(i)), thefluorescent screen 24 of the reflection high-energy electron diffractiondevice 2 is provided. Also, they may be expressed as the absolutecoordinates of the installation surface 25 on which the photoemissivemeans 15 is installed or they may be expressed as the relativecoordinates from the center of the filter 12.

[0104] The aforementioned are the series of processes used to computethe intensity decrease rate by using a point light source. Hereinafter,the present invention evolves into a series of processes used to correctthe intensity of the diffraction pattern, by using the computedintensity decrease rate. The process used to correct the intensity of adiffraction pattern will be explained next.

[0105] First, as in the aforementioned embodiment, the diffractionpattern is acquired optically, via photoreceptive means 11, while usingfilter 12. This diffraction pattern is obtained under the control of theintensity measurement means 32. The intensity measurement means 32transfers the measured intensity I_(C)(x_(i), y_(i)) of the diffractionpattern and its position coordinates (x_(i), y_(i)) to the measuredintensity storage means 35.

[0106] As shown in FIG. 6, the measurement intensity storage means 35stores by associating the measured intensity I_(C)(x_(i), y_(i)) and theposition coordinates (x_(i), y_(i)). Furthermore, although many measuredintensities I_(C) are preferable, it is suffices to measure according tothe position of the luminescent spot of the diffraction pattern targetedfor analysis.

[0107] Then, the corrected intensity computation means 36 receives themeasured intensity I_(C)(x_(i), y_(i)) and the position coordinates(x_(i), y_(i)) from the measured intensity storage means 35 and receivesintensity decrease rate T(x_(i), y_(i)) from the intensity decrease ratestorage means 34, after which it computes the corrected intensityI(x_(i), y_(i)) (i.e., the actual intensity), with the received positioncoordinates (x_(i), y_(i)) as the index. Then, the corrected-intensitycomputation means 36 transfers the corrected intensity I(x_(i), y_(i))to the external device 17, such as a display monitor or anothermeasuring instrument.

[0108] Here, the relationship among the measured diffraction pattern'smeasured intensity I_(C)(x_(i), y_(i)) and intensity decrease rateT(x_(i), y_(i)) and the corrected diffraction pattern's intensityI(x_(i), y_(i)) is as shown in the following Equation 2.

I(x _(i) , y _(i))=I _(C)(x _(i) , y _(i))×T(x _(i) , y _(i))  (2)

[0109] As explained previously, the present embodiment implements theintensity measurement means 32 that measures the intensity of the pointlight source measured by the photoreceptive means 11, via thehalation-prevention filter 12 that is varied so that its transmittanceincreases with the distance from the center, the intensity decrease ratecomputation means 33 that computes the decrease rate based on themeasured intensity and the reference intensity of the point light sourcewhen it does not pass through the halation-prevention filter 12, theintensity decrease rate storage means 34 that stores the decrease rate,the measured intensity storage means 35 that stores the diffractionpattern intensity measured by the photoreceptive means 11, via thehalation-prevention filter 12, and the corrected-intensity computationmeans 36 that computes the corrected intensity of the diffraction basedon the decrease rate stored by the intensity decrease rate storage means34, thereby enabling the correction of the diffraction pattern intensityobtained via the halation-prevention filter 12, according to theenvironment in which the halation-prevention filter 12 is used, andthereby enabling the acquisition of the precisely corrected orcalibrated intensity of the visible light actually emitted from thediffraction pattern of the fluorescent screen.

[0110] Here, the present embodiment is not limited to the aforementionedembodiments. For example, the correction of the diffraction patternintensity by means of the aforementioned procedure is not limited to thecorrection of intensity information represented by numbers of a specificunit system (e.g., candela), based on the obtained decrease rate.Instead of correcting numbers, it also is possible to correct theoptical intensity information by, for example, subjecting to imageprocessing the image information itself that indicates the diffractionpattern, based on the obtained decrease rate.

[0111] Also, although the present embodiment adopted a configurationthat is based on the first embodiment and is equipped with thephotoemissive means 15, the diffraction pattern intensity correctionmeans 16, etc., based on the first embodiment, it also is possible tosubstitute a configuration that is based on the second embodiment and isequipped with the photoemissive means 15, the diffraction patternintensity correction means 16, etc.

[0112] Moreover, the aforementioned diffraction pattern intensitycorrection program is not limited to a form such that it is installed ina so-called preinstalled form on a storage means (e.g., HDD). It alsomay be in the form such that it is stored in a compressed form as aninstallable program on a portable storage medium (e.g., CD-ROM,DVD-ROM), or in which it is installed as required on equipment (e.g., apersonal computer).

[0113] The deformation or distortion example of the aforementioned thirdembodiment will be explained with reference to FIG. 7. Here, componentswith the same structure as in the aforementioned embodiment are keyedwith the same symbols, so redundant descriptions are omitted. Also, FIG.7 is a functional block diagram of the diffraction intensity correctionmeans 18 of the present deformation example.

[0114] The present deformation example resulted from focusing on thefact that intensity analysis can be facilitated by adding, to a anycommercial intensity analysis program (i.e., software), a routine thatcorrects the intensity by using an equation with terms I(x, y) and T(x,y), as explained in a previous embodiment.

[0115] In an image analysis device for the filter 12, that does notrequire actual measurement for intensity correction when, for example,the predetermined specifications (e.g., the lens aperture and resolutionof the photoreceptive means 11) are already clear, it is possible toadopt a packaged configuration that embeds the correction details asdefaults.

[0116] To be specific, as shown in FIG. 7, as the aforementioneddeformation example of the third embodiment, the intensity correctionprogram may be one that utilizes, via a halation-prevention filter (notshown) that varies the transmittance when transmitting the visible lightemitted from the diffraction pattern of the fluorescent screen as theresult of reflection high-energy electron diffraction, so that it isminimal at the filter center and increases with the distance from thecenter, the diffraction pattern intensity correction means 18 thatimplements the measured intensity storage means 35 that stores theintensity, as measured by the photoreceptive means 11, of the visiblelight emitted from the diffraction pattern of the fluorescent screen,the intensity decrease rate storage means 37 that stores the rate ofdecrease of the intensity of the visible light transmitted through thehalation-prevention filter, and the corrected-intensity computationmeans 36 that computes the corrected intensity of the diffractionpattern by correcting the intensity stored by the measured intensitystorage means 35, based on the decrease rate stored by the intensitydecrease rate storage means 37.

[0117] Here, as aforementioned, the intensity decrease rate storagemeans 37 stores, as default correction parameters, the intensitydecrease rates appropriate to the specifications and the preset data forthe halation-prevention filter and the photoreceptive means 11.Furthermore, regarding the data structure of this intensity decreaserate storage means 37, the adopted structure is such that the intensitydecrease rate T(x_(i), y_(i)) and the position coordinates (x_(i),y_(i)) are related, instead of the measured intensity I(x_(i), y_(i))shown in FIG. 6.

[0118] Even if such a deformation example is used, it is possible tocorrect the intensity of the diffraction pattern obtained via thehalation-prevention filter and it is possible to obtain the intensity ofthe visible light actually emitted from the diffraction pattern of thefluorescent screen, because the following are implemented via ahalation-prevention filter (not shown) that is varied so that thetransmittance increases with the distance from the center: the measuredintensity storage means 35 that stores the diffraction pattern intensitymeasured by the photoreceptive means 11, the intensity decrease ratestorage means 37 that stores the rate of decrease in the intensity ofthe visible light transmitted through the halation-prevention filter,and the corrected-intensity computation means 36 that computes thecorrected intensity for the diffraction pattern by correcting theintensity stored by the measured intensity storage means 35, based onthe decrease rate stored by the intensity decrease rate storage means37. Furthermore, it provides an environment in which accurate intensityanalysis can be performed simply.

[0119] Next, comparative examples of the use and nonuse of thepreviously described halation-prevention filter will be explained, withreference to FIGS. 8 and 9. FIG. 8 is a photograph taken with a CCDcamera by means of a conventional method that does not use ahalation-prevention filter, of the reflection high-energy electrondiffraction pattern of an Si(111) single-crystal clean surface. FIGS.8(a), 8(b), and 8(c) are photographs taken with different exposuretimes. Meanwhile, FIG. 9 is a photograph of the reflection high-energyelectron diffraction pattern of a Si(111) single-crystal clean surface,which was taken with a CCD camera while using a halation-preventionfilter.

[0120]FIG. 8(a) is the diffraction pattern obtained with a 0.5-sec.exposure time. FIG. 8(b) is the diffraction pattern obtained with a1-sec. exposure time. FIG. 8(c) is the diffraction pattern obtained witha 2-sec. exposure time. Furthermore, the same diffraction patternnaturally is used as the target diffraction pattern.

[0121] In FIG. 8(a), the exposure time was insufficient, so there was nohalation in the vicinity of the specular reflection point(s). However,because the Kikuchi pattern outside the first Laue zone is dark as theresult of insufficient exposure, it cannot be determined.

[0122] If the exposure time is lengthened in order to determine theKikuchi pattern outside the first Laue zone, the variation is as shownin FIGS. 8(b) and (c). To be specific, as shown in FIG. 8(b), when theexposure time is lengthened to 1 sec., the Kikuchi pattern in thevicinity of the first Laue zone becomes identifiable. However, halationoccurs in the vicinity of the specular reflection point(s). Furthermore,when the exposure time is set to 2 sec. in order to verify the secondLaue zone, etc., not only the vicinity of the specular reflectionpoint(s), but also the inside of the zero-order Laue zone becomescompletely halated, as shown in FIG. 8(c).

[0123] By contrast, FIG. 9 shows the diffraction pattern when using ahalation-prevention filter with the filter gradation variation gradient(i.e., the transmittance variation) set to n=0.5. Furthermore, thephotographed diffraction pattern is the same as the diffraction patternin FIG. 8, and the CCD camera used for photography is also the same.

[0124] Then, under the conditions shown in the aforementioned FIG. 8,halation initially occurred in the vicinity of the specular reflectionpoint(s). In view of this, when the diffraction pattern shown in FIG. 9was photographed, the exposure time was set so that halation did notoccur in the vicinity of the specular reflection point(s), as acomparative example for the photograph shown in FIG. 8. Furthermore, theexposure time was 4 sec.

[0125] As shown in FIG. 9, when a halation-prevention filter was used,it was possible to clearly photograph up to the Kikuchi pattern thatappeared outside the second Laue zone, while maintaining a visible lightintensity in the vicinity of the specular reflection point(s), that wassimilar to that in FIG. 8(a).

[0126] The present invention is configured and functions asaforementioned, by varying the filter transmittance so that it is lowestat the filter center and increases with the distance from the center, itis possible to supply an environment that yields the entire diffractionpattern without halation, even though the entire diffraction pattern isacquired optically.

[0127] Also, because the transmittance increases in proportion to then^(th) power of r, the distance from the filter center, it is possibleto effectively and adequately reduce the light intensity in the vicinityof the center, compared with that in the periphery.

[0128] Furthermore, by varying the filter transmittance so that it islowest at the filter center and increases with the distance from thecenter, it is possible in the photoreceptive means to obtain theintensity of the visible light emitted from the diffraction pattern onthe fluorescent screen, within the allowable range of halation-freephotoreception.

[0129] Also, because the transmittance increases in proportion to then^(th) power of r, the distance from the filter center, it is possibleto effectively and adequately reduce the light intensity in the vicinityof the center, compared with that in the periphery.

[0130] The invention also has an in-plane or in-planar movement means,so it can provide a highly flexible halation-prevention mechanism thatcan respond to displacement of the specular reflection point(s) of thediffraction pattern.

[0131] The invention may provide an environment that enables accurateintensity analysis, because the rate of decrease in the intensity of thevisible light transmitted through the filter is computed, and thecorrected intensity resulting from the correction of the intensity ofthe visible light emitted from the diffraction pattern on thefluorescent screen is computed based on the decrease rate.

[0132] Also, the invention may provide a diffraction pattern intensityanalysis method that enables accurate intensity analysis, because it isequipped with a process that measures the intensity of a diffractionpattern via a halation-prevention filter that is varied so that thetransmittance increases with the distance from the center, a processthat obtains the intensity decrease rate attributable to the filter, anda process that corrects the intensity of the diffraction pattern, basedon the decrease rate.

[0133] In the present invention, because the transmittance increases inproportion to the nth power of r, the distance from the filter center,it is possible to provide a diffraction pattern intensity analysismethod that can analyze, without halation, the intensity of the visiblelight emitted from the diffraction pattern of a fluorescent screen.

[0134] Also, the invention implements a measured intensity storage meansthat stores the intensity of the diffraction pattern measured by thephotoreceptive means, via the halation-prevention filter varied so thatthe transmittance increases with the distance from the center, anintensity decrease rate storage means that stores the rate of decreasein the intensity of visible light transmitted through thehalation-prevention filter, and a corrected-intensity computation meansthat computes the corrected intensity of a diffraction pattern bycorrecting the intensity stored by the measured intensity storage meansbased on the decrease rate stored by the intensity decrease rate storagemeans, thereby making it easy to obtain the intensity of the visiblelight actually emitted from the diffraction pattern of the fluorescentscreen. Furthermore, it can provide simply an environment that enablesaccurate intensity analysis.

[0135] Furthermore, the invention implements an intensity measurementmeans that measures the intensity of the point light source measured bythe photoreceptive means, via the halation-prevention filter varied sothat the transmittance increases with the distance from the center, anintensity decrease rate computation means that computes the decreaserate based on the measured intensity and the reference intensity of thepoint light source when it does not pass through the halation-preventionfilter, an intensity decrease rate storage means that stores itsdecrease rate, a measured intensity storage means that stores theintensity of the diffraction pattern measured by a photoreceptive means,via the halation-prevention filter, and a corrected-intensitycomputation means that computes the corrected intensity of a diffractionpattern based on the decrease rate stored by the intensity decrease ratestorage means, so it enables the determination of the preciselycorrected intensity of the visible light actually emitted from thediffraction pattern of the fluorescent screen.

[0136] Accordingly, it is to be understood that the embodiments of theinvention herein described are merely illustrative of the application ofthe principles of the invention. Reference herein to details of theillustrated embodiments is not intended to limit the scope of theclaims, which themselves recite those features regarded as essential tothe invention.

What is claimed is:
 1. A halation-prevention filter for location along alight path connecting a fluorescent screen on which a diffractionpattern appears as a result of reflection high-energy electrondiffraction and a photoreceptive means that optically acquires saiddiffraction pattern, in which a transmittance of the visible lighttransmitted through the filter is minimum at a center of said filter andincreases with a distance from said center.
 2. The halation-preventionfilter of claim 1, characterized in that the transmittance increases inproportion to r^(n), where r is the distance from the filter center. 3.An image analysis device comprising: a fluorescent screen for creating adiffraction pattern that results from reflection high-energy electrondiffraction; a photoreceptor for optically acquiring the diffractionpattern that appears on the fluorescent screen; and ahalation-prevention filter for location along a light path connectingthe fluorescent screen and the photoreceptor, in which a transmittanceof the visible light transmitted through the filter is minimum at acenter of the filter and increases with a distance from the center. 4.The image analysis device of claim 3, in which the transmittance of thehalation-prevention filter increases in proportion to r^(n), where r isthe distance from the center of the filter.
 5. The image analysis deviceof claim 3 further comprising an in-plane movement means that moves thehalation-prevention filter in a plane orthogonal to the light path. 6.The image analysis device of claim 3, further comprising: a point lightsource; an emission controller for controlling the generation of lightby the point light source; an intensity measurement means for measuring,via the photoreceptor, the intensity of the visible light emitted fromthe diffraction pattern of the fluorescent screen and the intensity ofthe point light source-emitted visible light that passed through thefilter; an intensity decrease rate computation means for computing arate of decrease in the intensity of the visible light transmittedthrough the filter, based on the intensity of the visible light emittedby the point light source, that was measured by the intensitymeasurement means; and a corrected-intensity computation means that,based on the decrease rate computed by the intensity decrease ratecomputation means, computes the corrected intensity used to correct theintensity of the visible light emitted from the diffraction pattern ofthe fluorescent screen, that was measured by the photoreceptor.
 7. Adiffraction pattern intensity analysis method used to analyze intensityof visible light emitted from a diffraction pattern of a fluorescentscreen as a result of reflection high-energy electron diffraction,comprising the steps of: using a photoreceptor to measure the intensityof the diffraction pattern that appears on the fluorescent screen, via ahalation-prevention filter with a transmittance which is minimum at afilter center and increases with distance from the filter center; basedon a result of the measurement, obtaining a rate of decrease in theintensity of the visible light transmitted through the filter; andcorrecting the diffraction pattern intensity measured by thephotoreceptor, based on the decrease rate.
 8. The diffraction patternintensity analysis method of claim 7, in which the transmittance ofvisible light transmitted through the filter increases in proportion tor^(n), where r is a distance from the filter center.
 9. A diffractionpattern intensity correction program for use with an image analysisdevice having a fluorescent screen for creating a diffraction patternthat results from reflection high-energy electron diffraction, aphotoreceptor for optically acquiring the diffraction pattern thatappears on the fluorescent screen, and a halation-prevention filter forlocation along a light path connecting the fluorescent screen and thephotoreceptor, in which a transmittance of the visible light transmittedthrough the filter is minimum at a center of the filter and increaseswith a distance from the center, the program comprising: a measuredintensity storage means for storing an intensity of visible lightemitted from the diffraction pattern on the fluorescent screen as aresult of reflection high-energy electron diffraction, passed throughthe halation-prevention filter and detected by the photoreceptor means;an intensity decrease rate storage means for storing a rate of decreasein the intensity of the visible light transmitted through thehalation-prevention filter; and a corrected-intensity computation meansfor computing a corrected intensity of the diffraction pattern bycorrecting the intensity stored by the measured intensity storage means,based on the decrease rate stored by the intensity decrease rate storagemeans.
 10. The diffraction pattern intensity correction program of claim9, further comprising: a point light source; an emission controller forcontrolling the generation of light by the point light source; anintensity measurement means for measuring, via the photoreceptor, theintensity of the visible light emitted from the diffraction pattern ofthe fluorescent screen and the intensity of the point lightsource-emitted visible light that passed through the filter; anintensity decrease rate computation means for computing a rate ofdecrease in the intensity of the visible light transmitted through thefilter, based on the intensity of the visible light emitted by the pointlight source, that was measured by the intensity measurement means; anda corrected-intensity computation means that, based on the decrease ratecomputed by the intensity decrease rate computation means, computes thecorrected intensity used to correct the intensity of the visible lightemitted from the diffraction pattern of the fluorescent screen, that wasmeasured by the photoreceptor.